Increased physical activity in childhood has resulted in a large number of sports-related injuries. Although there is overlap between the sports-related injuries seen in pediatric and adult patients, important differences exist in the injury patterns of pediatric patients. These differences are related to the continuous changes in the developing skeleton and its relationship with adjacent soft tissues. The imbalance in strength between the growing bones and the nearby tendons and ligaments makes the bones prone to acute and chronic injuries. Acute injuries are more common in contact sports such as football and wrestling, whereas chronic injuries are often seen in baseball pitchers and gymnasts. Acute injuries unique to pediatric athletes include physeal fractures of the proximal and distal portions of the clavicle (periosteal sleeve fracture), the proximal humeral physis, and the coracoid process, as well as supracondylar, lateral condylar, and medial condylar fractures around the elbow. Chronic injuries, most commonly caused by repetitive microtrauma, include acromial apophyseolysis, Little Leaguer's shoulder, the constellation of findings seen in Little Leaguer's elbow, and injuries to the medial, lateral, and posterior elbow compartments. In addition, trochlear osteochondral lesions, gymnast's wrist, and rock climber's finger are less-common injuries that may be seen in children. In this article, the normal osseous development of the upper extremity is reviewed, with emphasis on the structures that are most commonly injured. The pathophysiology, imaging appearance, and imaging findings of pediatric athletic injuries are described, along with the prognostic implications. ©RSNA, 2016.